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    <title>Document</title>
    <script type="text/javascript">
        var mouth = parseInt(prompt("请输入要查找的月份"))
        switch (mouth) {
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                alert("该月有31天")
                break
            case 4:
            case 6:
            case 9:
            case 11:
                alert("该月有30天")
                break

            case 2:
                var year = parseInt(prompt("请输入年份"))
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    alert(year + "年2月有29天")
                    break
                } else {
                    alert(year + "年2月有28天")
                    break
                }

                default:
                    alert("请输入正确的年份（1-12）")
        }
    </script>
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